Method for the preparation of fusible lignin resins



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Patented July 13, 1954 METHOD FOR THE PREPARATION OF FUSELE LIGNINRESINS Hans Friedrich Miiller, Bregenz, Austria, assignor to InstitutInternational Financier of Eschen, Liechtenstein No Drawing. ApplicationMay 31, 1950, Serial No. 165,359

16 Claims. (Cl. 260-424) 1 2 The present invention relates to a noveland According to the invention this is achieved by particularlyadvantageous method for the prepafirst subjecting the raw materials toan alkali ration of fusible iignin resins from lignin, i. e. hydroxidetreatment which is known as such, lignin-containing raw materials, suchas woodsaid treatment being performed in such a manhydrolysis lignin,lignin-sulphonic acid, sulphite ner that the raw materials are mixedwith the waste liquor, peat, lignite and the like. alkali hydroxidesolution, dried therewith, and

Lignin is produced in the form of wood-hyheated to temperatures above100 centigrade at drolysis lignin and in the waste liquors of cel--least towards the end of the drying period. The lulose works in vastquantities every year, and dry material is then dissolved in water andthe no means have so far been found by which this iignin resinprecipitated from this fluid by acidiraw material might be utilized in asatisfactory fication. manner. Sulphite cellulose waste liquor, how- Itis a particular characteristic of this method, ever, is in part used forthe production of tan and one constituting considerable advantages, ninsand vanillin, and sulphate-liquor lignin for that mixtures of thelignin-containing raw mamoulded plates, but these processes utilize onlyterials may be used, such as a mixture of wood-2;.

hydrolysis lignin and lignin-sulphonic acid, preferably in theproportion of 1:5 to 1:10. It is The greatest obstacle to satisfactoryutilizaalso possible to use an alkali hydroxide dissolved tion of ligninis that the latter is formed in in sulphite cellulose waste liquor asalkali hydifferent states in different processes. Thus the droxidesolution, which, possibly after concenlignin of sulphite cellulose Wasteliquors is solutration, is mixed with insoluble lignin or ligninble inwater, sulphate liquor lignin is soluble in containing raw material.alkalis, Whilst wood-hydrolysis lignin is complete- It may further beadvantageous to add to the 1y insoluble. Accordingly, it has beenendeavalkaline solution other non-volatile alkaline cured to providespecial utilization processes for agents, such as alkali carbonate,alkaline earth every type of lignin so that a vast number of oxides andthe like in addition to or in partial diiferent utilization methods areknown today. substitution for, the alkali hydroxide. On the Profitableindustrial utilization of lignin will, other hand, lignin-solventmaterials, such as however, only be possible if ways and means arephenols, amines, monovalent or polyvalent alfound of utilizing thedifferent lignins on the 3{] cohols or the like may be added to thealkaline basis of uniform processes. In this respect the solution. wasteliquors of sulphite cellulose manufacture Furthermore, it is importantto keep the quanand wood-hydrolysis lignins must be considered tities ofalkali hydroxide and the heating temprimarily. The problem of theutilization of sulperatures in the decomposition process within phate iinin is not so acute since such iignin is such limits that on the onehand the lignin is not separated in the decomposition process. obtainedin a state in which it is completely It is a common characteristic ofall lignins that precipitable and fusible at least in boiling water,they consist of mixtures of high-molecularand that on the other hand nodecomposition weight materials which are transformed into occurs whichwould be detrimental to the precipresinous bodies under the influence ofhydrolyz- 4O itability of the lignin. ing reagents. In this respect manyprocesses In order to ensure uniform decomposition of have beensuggested employing phenols, or althe lignin it is advisable in thisprocess to effect kali hydroxides, or other suitable substances anddrying while the material is being mechanically endeavouring todetermine the conditions most kneaded and crushed. The drying processmay favourable for the individual lignin under confurther be effected instages, the temperature sideration. However, no process has hithertorising from step to step, while a vacuum may be become known in whichall possible lignins or applied in the first stage or stages. It isadvisaeven lignin mixtures can be worked into resins ble when dissolvingthe dried material obtained by means of one process. after alkalinetreatment, to use the minimum With the method according to the presentinquantity of water required therefor. vention, however, it is nowpossible to produce The alkaline decomposition Solutio y 13% fusible iinin resins from wood-hydrolysis iignin, precipitated by means of strongmineral acids, lignin-sulphonic acid, sulphite cellulose waste theliquid remaining after precipitation being liquor, peat, lignite andother iignin-containing used entirely or partly for dissolving the driedraw materials, said resins being eminently suited material, possiblyafter separation of the precipto a great variety of uses. itated salts.

a fraction of the available lignin. Wood-hydrolysis iignin is notutilized at all.

The alkaline decomposition liquid may, moreover, be precipitated bymeans of weak or medium acids such as carbonic acid or sulphurous acid,the precipitated lignin being treated with a strong mineral acidsubsequent to its separation from the solution. The precipitation is insuch cases preferably effected at temperatures ensuring that the ligninis precipitated in a fused state.

The liquid remaining after precipitation of the lignin with weak ormedium acids may be added to another decomposition batch aftercausticization with calcium oxide and separation of the limeprecipitate. The waste liquor produced after precipitation of the ligninmay be treated, if necessary after several repetitions of its use fordissolving the alkali treated lignin product, by means of concentratedmineral acids. Also the lignin remaining in the waste liquor beprecipitated only subsequent to crystallization and separation of thealkali salts.

The liquor remaining after precipitation of the lignin by means of weakor medium acids may, on the other hand, also be causticized with calciumoxide after evaporation of water and roasting off of the organicsubstances, and added to a new decomposition batch after separation ofthe lime precipitate. Alternatively, the solution remaining afterprecipitation of the lignin may be added to a new decomposition batchafter causticization of the alkali salts and the remaining liquorobtained after precipitation of the lignin may be roasted, causticizedand added to a new decomposition batch after filtering, possibly onlyafter several repetitions of the liquor recovery.

When moist, the lignin precipitated by means of acid, or parts of saidlignin, may be mixed, possibly with lignin-dissolving materials, such asmonovalent or polyvalent alcohols, esters, ethers, ketones or the like,or condensible plastic components, such as phenols, amines, amides,aldehydes, ketones or the like, or with plastics produced bycondensation or mixtures of such substances.

The acid-precipitated fusible ligin resin may, after addition ofalkaline agents, be used in known manner in the manufacture of mouldingcompounds, ply-wood, laminated wood, fibre plates, chip plates or thelike, if necessary after mixing with lignin-solving or condensableplastic components, or plastics produced by condensation, or mixtures ofsuch materials, said lignin being used for said purposes either alone,in solution, suspension, or in the form of a glue film or powder as aheat-hardenable binding agent.

Alternatively it may be preferred to add the acidprecipitated fusiblelignin resin in its moist state to acid-hardening plastics, if necessarywith the addition of lignin-dissolving materials or condensable plasticcomponents or mixtures of such materials, for use in the known manner asa heat-hardenable binding agent in the manufacture of mouldingcompounds, ply-Wood, laminated wood, fibre plates, chip plates or thelike either alone, in solution, suspension, or in the solid state as afilm or powder.

By means of the described method according to this invention it ispossible, as stressed above, to produce the same final product fromvarious raw materials by means of one and the same process. Theindividual material groups undergo the following changes:Lignin-sulphonic acid is desulphonated by alkali hydroxide and changedinto a water-insoluble fusible resin with concomitant decomposition.

The insoluble and Fill non-fusible wood-hydrolysis lignins arehydrolytically cleaved and decomposed and then also form aWater-insoluble and fusible resin. With the raw materials containingmostly lignin besides carbohydrates, such as peat, the carbohydrates arechanged into water-soluble decomposition products, the lignin beingseparated as a resin. The following remarks apply in connection with thereaction conditions to be adhered to in these processes.

The quantities of alkali and drying temperatures must be adapted to thefinal product desired. In this respect it is advisable, particu larlyfor reasons of economy, to employ the minimum of alkali and a dryingtemperature which is as high as possible. If the quantity of alkalihydroxide employed is not sufficient and the heating temperature nothigh enough, the lignin is not sufficiently decomposed. It retains itshigh molecular weight and cannot be fused. In the case of ligninsulphonic acid there is the added fact that the desulphonation is noteffected completely under conditions which are too mild, so that thelignin precipitates incompletely when the acid precipitation takes placesubsequent to alkaline decomposition. On the other hand it is notadvisable to decompose the lignin too drastically since a portion of thelignin would be destroyed or at least changed into water-solublelow-molecular-weight substances which largely remain in solution duringthe precipitation of the lignin, and greatly impair the technicalapplication of lignin resin insofar as they are actually precipitated.Accordingly it is a characteristic of the best possible reactionconditions in every case, if lignin is obtained in maximum quantitiesand in a fusible condition.

If the heating temperature in the drying process is high, e. g. 200centigrade and higher, there is the danger, in particular with thehighly reactive lignin obtained in hydrolysis by means of hydrochloricacid, that the dried product ignites spontaneously. This may be avoidedby adding less reactive alkaline substances, such as sodium '2 carbonateor calcium oxide, to the decomposition solution. In such cases a thinsalt layer forms on the surface of the dried material and preventscombustion. On the other hand the decomposition activity of the alkalihydroxide may not be high enough, as may be the case with highlycondensed wood-hydrolysis lignins. In such a case the decompositioneffect may be intensified by addition of lignin-dissolving substances,in particular phenols, or amines, alcohols, glycols, ketones or thelike.

Apart from the adaptation of the decomposition agents to the rawmaterial and the final product desired, the following measures are ofimportance.

1. Prior to decomposition it is advisable to steep the lignin-containingraw material as a fine powder uniformly with the alkali hydroxidesolution. If there is a tendency on the part of the drying material tocrust, said material wiil have to be worked in a very thin layer or withcontinuous stirring.

2. The lignin resin may be precipitated from the alkaline decompositionsolution by means of strong Or weak acids. Precipitation by means ofstrong acids does not impair the product. On the contrary, it isadvisable to treat the resins precipitated by means of weak acids withstrong acids, since the lignin resin may otherwise remain partiallywater-soluble.

3. The decomposed lignin is precipitated from a solution which is asconcentrated as possible. Owing to the salt concentration thenprevailing, a high yield of lignin resin is obtained and also thelow-molecular-weight resin components are precipitated which are ofimportance for the fusibility of the resin obtained.

4. Precipitation may be effected at elevated temperature and the ligninis separated in a fused state. Thus excessive contamination of thelignin resin by inorganic salts may be avoided. Moreover, time-consumingfiltering processes can be dispensed with.

It is a particular advantage of the method according to the inventionthat it permits or the preparation of mixtures of raw materials, inparticular mixtures of fluid sulphite waste liquor and insolublewood-hydrolysis lignin, peat or the like. Thus two purposes areachieved. First, the waste liquor may be used in its fluid state, thealkali hydroxide may be dissolved therein, and the pulverized, insolubleligneous raw materials be steeped in this solution. On the other hand,the addition of insoluble materials to the waste liquor ofiersparticular advantages. Above all, the evaporation rate of the wasteliquor is substantially raised and crust formation avoided, so that thedecomposition takes place in a fraction of the time required whensulphite waste liquor is used alone.

With regard to the apparatus required, the decomposition methodaccording to this invention afiords considerable'advantages over themethods hitherto applied, since it permits of the use of simpleapparatus which is available everywhere, avoids pressure vessels, and,above all, the process of decomposition may be effected continuously. Inthe event of the alkali-treated ligneone material forming a coherentmass while drying, a cylinder drier heated to approximately 200centigrade surface temperature is advantageously used. In such a case,however, the material can be applied in a thin layer only, On the otherhand, there is the possibility of pre-drying the material in a thickerlayer on the cylinder drier, then crushing it and subsequently heatingit to a higher temperature in a tunnel kiln. If the material forms aloose mass, a revolving tubular kiln, possibly with a ball charge, maybe employed. The metallic heating surface of the drier is then suitablymade of corrosiomproof material 3 instead of iron so that the driedmaterial does not stick to the surfaces.

A further particular advantage of the decom position method according tothe invention is deserving of special mention: a dense product resultsfrom the alkaline drying. This results in that the alkaline dried mattermay be dissolved in a very high concentration, which fact aifords theadvantage, as aforementioned, that the lignin resin may be precipitatedwith a high yield.

If the lignin resin is precipitated from the alkaline solution by meansof carbonic acid or sulphurous acid the waste liquors obtained may beused again. Precipitation by these gaseous acids may be effected binjecting the gases into the hot alkaline lignin solution. However, itis also possible to atomize the solution into a stream of the acid gas.When all the alkali hydroxide, for instance, sodium hydroxide, has beenconverted into the acid salts of the acids, a black lignin resinprecipitates. The solution remaining after precipitation of said resincontains sodium bicarbonate and sodium bisulphite respectively and thelow-molecular-Weight sodium salts of the lignin decomposition productsand 6 'v carbohydrates. If quicklime is added to this solution and thelime slurry filtered ofi, the solution will contain a mixture of sodiumhydroxide and organic sodium salts. When this solution is brought to theconcentration required for the lignin decomposition by addition of freshsodium hydroxide, it may be used for a further decomposition processWithout attendant disadvantage. By re-using the liquor, so much sodiumhydroxide will in this case be saved as remained unused in the firstlignin decomposition. If the waste liquor is repeatedly re-used in thismanner, the organic sodium salts become concentrated in the liquors andprogressively deleteriously afiect decomposition. Eventually the entirewaste liquor must be evaporated, roasted, dissolved in water, andcausticized with quicklime; a cleaned sodium liquor is thus obtainedwhich may again be reused in the decomposition process.

In the event that a part of the lignin components are retained in thewaste liquors, as may be the case in the precipitation by means ofcarbonic acid, one may also proceed in such a manner that the inorganicsodium salts are allowed to crystallize out of the waste liquor,acidifying the solution obtained after separation of these salts. Thelignin contained in the Waste liquor is then precipitated as a thinlyliquid resin.

The lignin resin precipitated by means of strong acids, or precipitatedby means of weak acids and subsequently acidified, must be furthertreated in its moist state. Should it be C0111 pletely dried, it willirreversibly lose the greater part of its fusibility and solvability inorganic substances.

If it is desired to use the lignin resin as a heathardening bindingagent, its fusibility and ability to be liquified may be increased bythe addition of lignin-dissolving substances, such as alcohols, glycols,glycerin, glycerin esters, and other ters, ethers, ketones or the like.However, the addition of lignin-dissolving substances must not be toolarge, since the hardenability of the resins when heated may beimpaired. In like manner lignin-dissolving and at the same timecondensable substances, such as phenols, amines, amides or the like havesimilar effects, and they may be used in combination with aldehydes andketones. Mixtures of polyvalent phenols, amines or amides are even morefavourable, since they may condense with the lignin on the one hand, andwith the aldehydes or ketones on the other. Even when added in smallquantities, aldehydes alone, such as formaldehyde, hexamethylenetetramine, acetaldehyde, furfural and the like, effect an improvement inhardenability. The most favourable effects are obtained, however, ifheathardening plastics are added, preferably in their initialcondensation state. The lignin modified plastics thus obtained mayreplace the pure plastics in a large number of uses, such as inmanufacture of moulding compounds, ply-wood, laminated wood, fibre andchip plates and the like.

If alkaline-hardening plastics are being combined with the lignin resin,alkaline agents, such as alkali hydroxides, alkaline earth oxides,magnesium oxides or the like or mixtures of such substances must beadded to the mixture prior to further operations.

However, if the lignin resin is used in conjunction with acid-hardeningplastics, the solution obtained may be used as it is.

The method according to the invention, 1. e. the

method of mixing the raw materials with alkali hydroxide solution, ofdrying them with it, and of heating them, at least towards the end ofthe drying process, to temperatures above 100 centigrade, then ofdissolving the dried material in water, finally precipitating the ligninresin by acidification, may be employed with particular advantage in theprocess of treating the waste liquors obtained in the decomposition ofcellulose-containing materials.

Examples of application 1. 1000 grams finely-ground lignin obtained inwood hydrolysis with concentrated hydrochloric acid (Bergius Process) isthoroughly mixed with 400 grams of sodium hydroxide and 1000 grams ofwater, dried in a rotary tubular kiln with a steelball charge at 220centigrade wall temperature, and heated until no more water escapes anda sample of the dried mixture is readily and completely soluble inwater. The dried product is stirred into 2000 cubic centimetres of waterand stirred while heating until all has dissolved. Stirring quiterapidly, 30% sulphuric acid is added to the lignin solution while at atemperature oetween 60 and 90 centigrade until a pH value of 3 isobtained. On precipitation, the lignin agglomerates in the solution andis fused together in the solution by further heating. The cooled ligninresin, which is separated from the solution, is then crushed and workedinto a fine suspension with 350 cubic centimetres of water. Thissuspension is heated to boiling point and a purified lignin resin isthus obtained.

If it is desired to mix the lignin resin with e. g. a phenolformaldehyde resin, the process is as follows: A resin is produced byboiling 200 grams of phenol, 240 grams of 30% formaline and 1 gram ofsodiumhydroxide for two hours. Without separating the phenolic resinfrom the separated water, it is stirred when cold into the said ligninresin emulsion. The mixture is then heated, the lignin modified phenolicresin separates in its fused state, and the water is removed.

If it is desired to produce a moulding compound with the lignin resindescribed, the resin is mixed while being heated with 50 grams glycerineand 5 grams sodium hydroxide dissolved in 100 cubic centimetres ofwater, pouring the hot mixture in a heated kneader charged with 900grams wood meal, 100 grams kaolin and 20 grams magnesium oxide. Now thematerial is kneaded at increasing temperature until a plastic mixture isobtained.

2. 1000 grams finely-ground Bergius lignin is mixed, as described under(1) with sodium hydroxide and heated. The dried material is dissolved in2000 cubic centimetres of water, heated to a temperature of 60centigrade, and a strong flow of carbonic acid in very fine distributioninjected until the lignin is separated as a black resin and the solutionhas acquired a pH value of 8.5 The lignin resin is separated from thesolution, suspended in water after crushing, then 30% sulphuric acid isadded until a pH value of 3 is obtained. The liquor remaining after thecarbonic acid precipitation is heated, and sun-lcient calcium oxiderequired for the transformation of the sodium bicarbonate added and thecalcium carbonate precipitate filtered oiT after vigorous stirring. Then180 grams sodium hydroxide is added to the thus regenerated liquor,which is then mixed with 1000 grams Bergius lignin, and thedecomposition effected in the manner hereinabove described.

3. 1000 grams finely-ground Bergius lignin is decomposed with sodiumhydroxide as described under (1). The lignin resin is precipitated bymean of carbonic acid in the manner described under (2) and treated withmineral acid. The remaining liquor is evaporated in vacuo, fully driedsubsequently and roasted until no organic substance remains. Theresidual salt deposit is taken up in Water, calcium oxide being added tothe solution, which is then filtered. The clear alkaline liquor is usedfor the decomposition of a further 1000 grams Bergius lignin after anaddition of 125 grams sodium hydroxide.

4. 1000 grams finely-ground lignin obtained by wood hydrolysis by meansof sulphuric acid is mixed with 500 grams sodium hydroxide, 1200 gramswater and 50 grams phenol, dried in the rotary tubular kiln, heated, andthe dried product is dissolved in 2500 cubic centimetres of water. Onprecipitation with mineral acids a fusible lignin is obtained and isworked up in accordance with Example 1.

5. 500 grams finely-ground peat is intimately mixed with a solution of150 grams sodium hydroxide in 300 cubic centimetres of water. Then 100grams 50% sulphite waste liquor is mixed with a solution of 200 gramssodium hydroxide in 200 cubic centimetres of water and the mixture isadded to the peat treated with liquor. After prolonged mixing of allingredients the paste like material is placed on a cylinder drier fromwhich the water quickly evaporates and on which a continuous layer isformed. This product is the addition of 500 cubic centimetres of water.

Then sulphuric acid is added until a low pH value is reached, and thelignin resin precipitated by heating the solution.

6. An alkali solution is prepared from 420 grams of sodium hydroxide and400 grams of water, and added to 2000 grams sulphite waste liquor andthe resulting solution is completely dried in a thin layer on a cylinderdrier heated by steam at a gauge pressure of 10 atmospheres. The drythin layer of material is finely ground in a high-speed mill. The driedproduct is dissolved in 200 cubic centimetres of water, the ligninprecipitated at centigrade by means of sulphurous acid and separatedfrom the solution. As described in Example 5, a suspension is made with250 cubic centimetres of water, the lignin is acidified and fused byheating. If necessary, the lignin resin may again be suspended and fusedby heating.

I claim:

1. The process of preparing fusible lignin resins from lignin,wood-hydrolysis lignin, lignin-sulphonic acid, sulphite waste liquor,peat and lignite, comprising mixing at least one of the said ligneousmaterials with sufiicient alkali metal hydroxide in strong aqueoussolution to react with all'the lignin present, the proportions being ofthe order of 40 to 400 parts by weight of the alkali metal hydroxide perparts by ucl ht of lignin, heating the moist mixture to temperaturessubstantially above 100 C. but less than 200 C. to evaporate themoisture and to produce a dry residue substantially completely solublein water, dissolving the said dry residue in water and adding mineralacid in an amount sufficient to precipitate fusible lignin resin.

2. The process according to claim 1 wherein the ligneous materialcomprises a mixture of the lignin residue derived from the acidhydrolysis of wood and lignin sulphonic acid in weight proportions offrom 1:5 to about 1:10.

3. The process according to claim 1 wherein the alkali metal hydroxideis dissolved in sulphite cellulose waste liquor before being admixedwith other ligneous material.

4. The process according to claim 1 wherein part of the alkali metalhydroxide is replaced by a compound taken from the group consisting ofcarbonates and oxides of the alkali and alkali earth metals.

5. The process according to claim 1, wherein a solubilizing agent forthe lignin is added to the mixture or" ligneous material and alkalimetal hydroxide.

6. The process according to claim 1, wherein phenol is added as asolubilizing agent for the alkali reacted lignin, at about a ratio of 5parts by weight per 100 parts by weight of lignin.

7. The process according to claim 1, wherein to the aqueous solution ofthe said dry residue gaseous carbonic acid is added to precipitatefusible lignin resin.

8. The process according to claim 1, wherein the aqueous solution of thesaid dry residue is saturated with gaseous sulphurous acid toprecipitate fusible lignin resin.

9. The process according to claim 1, wherein the aqueous solution of thesaid dry residue is heated to a temperature between 60 to 90 C. whilethe said mineral acid is added.

10. The process according to claim 1, wherein the said moist mixture ofligneous material and alkali metal hydroxide is broken up during thedrying to obtain the residue in form of a powder.

11. The process according to claim 1, wherein the said moist mixture ofligneous material and alkali metal hydroxide is initially dried undervacuum and thereafter under atmospheric pressure.

12. The process according to claim 1, wherein to the aqueous solution ofthe said dry residue 30 per cent sulphuric acid is added to precipitatefusible resin.

13. The process of preparing fusible lignin resins from lignin,wood-hydrolysis lignin, lignin- Lil 7 adding mineral acid in an amountsufficient to precipitate fusible lignin resin, separating theprecipitated lignin resin from the liquid portion, subjecting the liquidportion to a lime treatment, separating the precipitate and mixing theremaining liquid with a new portion of one of the said ligneousmaterials.

14. The process according to claim 13, wherein the aqueous solution ofthe said dry residue is treated with a weak mineral acid and theprecipitated lignin resin is separated from the liquid portion, brokenup into small particles and suspended in water which is acidified to apH of 3 by means of sulphuric acid.

15. The process according to claim 13, wherein the liquid portionremaining after the said acid treatment and the separation ofprecipitated lignin resin is evaporated in vacuo to a residue which,after drying and roasting to destroy organic impurities, is redissolvedin water, in order to use the said aqueous solution, after a limetreatment and filtration, for the preparation of a new batch of fusiblelignin resin from one of the said ligneous materials.

16. The process according to claim 13, wherein gaseous carbonic acid isused to precipitate lignin resin from the said aqueous solution of theresidue, causing alkali metal salts to crystallize from the liquidportion remaining after the separation of precipitated lignin resin,separating the said crystallized salts and adding strong mineral acid tothe remaining liquid to precipitate residual quantities of lignin resin.

References Cited in the file of this patent UNITED STATES PATENTSMangold et al. July 8, 1951

1. THE PROCESS OF PREPARING FUSIBLE LIGNIN RESINS FROM LINGNIN,WOOD-HYDROLYSIS LIGNIN, LIGNIN-SULPHONIC ACID, SULPHITE WASTE LIQUOR,PEAT AND LIGNITE, COMPRISING MIXING AT LEAST ONE OF THE SAID LIGNEOUSMATERIALS WITH SUFFICIENT ALKALI METAL HYDROXIDE IN STRONG AQUEOUSSOLUTION TO REACT WITH ALL THE LIGNIN PRESENT, THE PROPORTIONS BEING OFTHE ORDER OF 40 TO 400 PARTS BY WEIGHT OF THE ALKALI METAL HYDROXIDE PER100 PARTS BY WEIGHT OF LIGNIN, HEATING THE MOIST MIXTURE TO TEMPERATURESSUBSTANTIALLY ABOVE 100* C. BUT LESS THAN 200* C. TO EVAPORATE THEMOISTURE AND TO PRODUCE A DRY RESIDUE SUBSTANTIALLY COMPLETELY SOLUBLEIN WATER, DISSOLVING THE SAID DRY RESIDUE IN WATER AND ADDING MINERALACID IN AN AMOUNT SUFFICIENT TO PRECIPITATE FUSIBLE LIGNIN RESIN.